Thermal expansion and crystal structure of FeSi between 4 and 1173 K determined by time-of-flight neutron powder diffraction

The thermal expansion and crystal structure of FeSi has been determined by neutron powder diffraction between 4 and 1173?K. No evidence was seen of any structural or magnetic transitions at low temperatures. The average volumetric thermal expansion coefficient above room temperature was found to be 4.85(5)?×?10^?5?K^?1. The cell volume was fitted over the complete temperature range using Grüneisen approximations to the zero pressure equation of state, with the internal energy calculated via a Debye model; a Grüneisen second-order approximation gave the following parameters: θ_D=445(11)?K, V ₀=89.596(8)?ų, K ₀′=4.4(4) and γ′=2.33(3), where θ_D is the Debye temperature, V ₀ is V at T=0?K, K ₀′ is the first derivative with respect to pressure of the incompressibility and γ′ is a Grüneisen parameter. The thermodynamic Grüneisen parameter, γ_th, has been calculated from experimental data in the range 4–400?K. The crystal structure was found to be almost invariant with temperature. The thermal vibrations of the Fe atoms are almost isotropic at all temperatures; those of the Si atoms become more anisotropic as the temperature increases.     

桥梁限位器抗震设计方法研究

本文建立了两跨简支梁桥和五跨多跨刚架桥两结构模型，针对限位器的种类、刚度、强度、安装位置，输入地震动等进行了大量工况下的数值模拟研究。研究表明限位器与柱（框架）的刚度比在0.5-2之间较优。将现有的限位器设计方法应用于两算例结构，对现有限位器设计方法进行了比较研究。     

区位进入理论与企业集团的国际化扩张——以海尔集团为例

中国企业集团是改革开放以后出现的大型企业组织 ,在经济全球化的背景下 ,研究其国际化扩张具有重大现实意义。本文在详细介绍Hayter的国际企业区位进入理论的基础上 ,以海尔集团为例 ,分析了企业集团的国际化扩张过程 ;其次 ,分析了海尔集团所具有的进入优势以及所面临的空间进入壁垒。海尔集团所具有的进入优势有管理与文化优势、技术创新优势、产品质量优势、营销优势 ,但还面临着心理距离、企业规模小以及东道国政策的限制等空间壁垒。最后 ,提出了有关企业集团国际化扩张的一些对策。     

AGRICULTURAL EXPANSION IN NORTHERN ALBERTA

ABSTRACT. Since the early 1980s some 40,000 acres of forested land have been cleared and placed under cultivation by Mennonite farmers near the small town of La Crete in northern Alberta's Peace River district. This incipient agriculture has been accompanied by dramatic increases in road building and home construction and by the establishment of churches and schools. The principal force behind the acquisition of land has been a desire of families to have homes in rural areas where they can enjoy lifestyles based on traditional Mennonite values. Because most new farmers cannot earn a living in the district from agriculture alone, they must rely on the wood industries to supplement their incomes. Demand is building for the province to open still more land, but disagreements between the government and the Mennonite community about the most appropriate location for developing new farms has put further expansion on hold until the conflict can be resolved.     

旅游生态环境容量的经济学探讨

在总结旅游环境容量研究进展的基础上，提出了研究旅游环境容量意义及其概念体系，并就影响旅游环境容量的关键性因子－旅游生态环境容量进行了分析，运用经济学的理论和方法，提出了引起旅游生态环境容量的深层原因是外部不经济性，最后就为了实现资源环境的可持续发展，应该从法律、行政，经济、社会等角度对社会各利益加以协调，构建了有效的制度平台和相应的措施，使外部成本内部化，并提出了解决这些问题的具体对策和建议。     

THE EFFECTS OF EXTERNAL FORCING,DISSIPATION AND NONLINEARITY ON THE SOLUTIONS OF ATMOSPHERIC EQUATIONS*

Based on the primitive equations of the atmosphere,we study the effects of external forcing.dissipation and nonlinearity on the solutions of stationary motion and non-stationary motion.The results show that the asymptotic behavior of solutions of the forced dissipative nonlinear system is essentially different from that of the adiabatic non-dissipative system,the adiabatic dissipative system,the diabatic non-dissipative system and the diabatic dissipative linear system,and that the joint action of external forcing,dissipation and nonlinearity is the source of multiple equilibria.From this we can conclude that the important actions of diabatic heating and dissipation must be considered in the models of the long-term weather and the climate.     

台风区和外围暴雨区的旋转风、散度风动能收支

用完全的散度风(v_D)和旋转风(v_R)动能收支方程对8116台风和8407台风以及8116台风与其外围暴雨区的关系作了讨论。结果表明:台风区的有效位能通过散度风动能(K_D)转换为旋转风动能(K_R).台风向区域外部输出动能,在暴雨区上空通过涡度、散度场相互作用的转换机制由K_R向K_D转换,散度风加大触发对流发展产生暴雨,这可能是台风与其外围暴雨联系的一种能量过程。     

利用遥感监测和分析珠江三角洲的城市扩张过程——以东莞市为例

伴随着经济的快速增长,珠江三角洲近年来出现了迅速的城市化以及乡村城市化的过程。沿着城镇边缘和公路两旁,大片的农田被侵占来单方面地满足城市开发的需要,忽略了粮食产量减少以及环境质量恶化等问题。利用遥感可以有效地监测珠江三角洲的城市扩张过程。在遥感多时相监测的基础上通过熵的计算,可以定量地描述城市扩张的空间规律及扩散过程。     

Estimating Climate-Change Impacts on Colorado Plateau Snowpack Using Downscaling Methods

This study develops observed climate-based downscaling transfer functions that are used with general circulation model (GCM) output to assess potential global-change impacts on Upper Colorado Plateau, USA, water resources. Daily automated snow water equivalent stations are used with 700 mb atmospheric circulation to determine empirical transfer functions. Downscaling methodologies using multiple regression and neural networks are evaluated, with the neural network results explaining approximately 70%of the daily snowfall variance. The neural network-based transfer functions are used with the GENESIS GCM to simulate snowfall characteristics in both a 1xCO₂ and a 2xCO₂ climate. While the total precipitation simulated by the 2xCO₂ analysis remains nearly the same as today, less will fall as snow; specifically, snow water equivalence shows significant reduction (except in the Green River Basin) as the snow season is reduced by 58 days on average.     

瞬变电磁场的奇点展开法

在分析电磁系统自然谐振现象的基础上,简述了瞬变电磁场奇点展开法的物理基础、基本理论、极点提取方法,并考查了奇点展开法在地球物理中的应用可能性。